Tips for electrosurgical use are subject to high temperature at least whereat the electrosurgical arc emanates during, e. g. fulguration or coagulation. The heat thus provided by ohmic coupling through air causes the proteins in the bodily fluids to coagulate and adhere to the tips.
Coatings have been used to increase the ease of cleanability of the electrosurgical tips. U.S. Pat. No. 4,785,807 has a primer and top coating of Teflon polymer over an etched or abraded stainless steel tip. The coating is thin and during application of electromagnetic energy it is said that there is capacitive coupling to allow passage of power to the tissue being treated. Thus, the Teflon polymer surface should remain largely intact and so the cleanability of the tip is good.
U.S. Pat. No. 4,492,231 discusses temperature, tip conductivity and sticking of desiccated blood in a bipolar forceps.
U.S. Pat. Nos. 4,232,676 and 4,314,559 assigned to Corning Glass Works, disclose mechanically cutting knives or scalpel tips that have areas for electrocautery and other areas which do not conduct high frequency power. The '676 patent has bipolar electrodes on the same tip so that power passing therebetween will cauterize bleeders thereagainst. The '559 patent is an electrically conductive coating over a glass scalpel to which a silver brazing paste has been applied forming a surface finish having interstices to be filled with Teflon polymer for providing non-stick properties. Alternately, platinum is applied with a rough and Teflon polymer filled surface. Only portions of the scalpel that are covered have an electrical connection between them and the tissue; the silver or platinum conductors have numerous problems. Most importantly, these noble metals are expensive and applied in a relative thin layer which must be mechanically compatible with the electrosurgical blade or tip. In use the surgeon may flex the blade during cleaning as for example, while wiping the used tip on a cleaning pad, patient drape or the like. Good mechanical connection between the conductive layer and the glass substrate is essential to prevent fracture of the coating or still worse flaking of the coating into the wound. The glass substrate is not a deformable material and would fracture under bending and therefore be unacceptable for use in surgery. In addition, biocompatability of the conductive layer and the tissue is critical to a commercial product and silver is not an endorsed material for contact with a wound. No commercially viable method of making is taught in '559. Consequently, a conductive layer that is metallurgically, mechanically and electrically compatible and biocompatable has not been known. The platinum conductive layer in the '559 patent was found to adhere poorly, be expensive and therefore unacceptable.
The Teflon polymer fills interstices, inclusions and the like at the surface providing non-stick areas on the cutting, cauterizing or coagulating instrument. The '559 patent teaches of a surface which provides areas of Teflon polymer and raw metal and so recognizes the conductive nature of the tip and permits energy flow without capacitive coupling or the need to overcome the electrical insulative properties of the polymer coating. Specifically, interstices along the conductive layer on the substrate of the metal tip are filled with primer and a top coat of Teflon polymer. The surface is thus partly conductive metal and partly cleanable Teflon polymer but the problems of compatibility with known conductive layer materials have hampered commercially successful blades.
Cookware has been made with filled fluoropolymer to reinforce the relatively soft polymer against scrapes and abrasions. In particular, fillers such as mica and other minerals, metals, ceramics and other materials have been used for that purpose and to improve the appearance of the coated cookware. There is no electrosurgical energy conducted in cookware. No partially coated electrosurgical electrodes exist wherein an easily cleaned electrosurgical electrode having a partial coating of fluorinated polymer including areas of exposed and compatible metallic conductor therethrough and uniformly distributed thereabout for providing an effective conductive and cleanable electrode are known in the prior patents. It has been found that the cleanability of the electrosurgical tips is a function of surface finish as well as the surface free energy of the partial coating. The burning through the fully coated electrosurgical electrodes has been a problem which is corrected by the partially coated electrode disclosed and claimed herein. Significant reductions of adherence of coagulum to the electrosurgical electrode is possible with the partially coated blade.